Fuel that evaporates from fuel storage and delivery systems of various devices, including vehicles, equipment, and tools that use internal combustion engines, has the potential to contribute a significant portion of ozone-depleting emissions into the atmosphere. Various regulatory agencies seek to reduce evaporative emissions by requiring manufacturers of these devices to comply with regulations as a condition for offering their products for sale in the agency's jurisdiction. These regulations have led to the development and implementation of systems that capture evaporative emissions. A substantial portion of the regulatory effort focuses on capturing and controlling evaporative emissions from passenger vehicles with internal combustion engines.
Evaporative emissions are typically generated when stored fuel, generally from a fuel tank or other fuel storage device, evaporates and escapes into the atmosphere. Manufacturers of vehicles and other products that use internal combustion engines are required by law to implement systems that capture evaporative emissions and prevent their release into the atmosphere. Evaporative emissions control systems are designed to ensure that fuel vapors from the fuel storage tank of a vehicle are not emitted into the atmosphere, but are captured, stored, and subsequently used by the vehicle, in compliance with regulatory standards. Evaporative emissions control systems are typically used on vehicles and other products, and comprise a fuel vapor storage device, referred to as an evaporative canister, that has a fluid connection a fuel storage tank, and a fluid connection to an intake of the internal combustion engine. The evaporative canister is a sealed container that includes a predetermined volume of adsorbent material for adsorbing fuel vapors. Evaporated fuel vapors (typically hydrocarbons) are inlet to the canister through a vapor inlet port that is attached to the fuel tank. There is a purge port in the canister that is fluidly attached via tubing to an inlet of the intake of the engine. There is a fresh air inlet to the canister. There are other devices on the canister, including valves and sensors, which are necessary for complete operation and diagnosis of the canister and evaporative system. In operation, fuel vapors flow with air from the fuel storage system to the canister and are adsorbed onto the adsorbent material. Flow is caused by increased pressure that is created in the fuel storage system as the fuel evaporates. When operating, the intake of the engine typically generates a negative pressure that may be used to cause flow of air from the fresh air inlet through the canister and into the engine. When air flows through the canister the adsorbed fuel vapors are desorbed from the adsorbent material and flowed into the engine intake, wherein they are burned by the engine as part of ongoing engine operation. There are other aspects of the evaporative system, including diagnostics and on-board vapor recovery systems that are part of the operation of the evaporative system but not directly affected by the specific invention.
Demonstration of compliance to regulatory emissions standards includes subjecting the device, typically a motor vehicle, to predetermined test conditions and measuring the net generation of evaporative emissions. The regulatory agencies, including the California Air Resources Board (“ARB”) and the United States Environmental Protection Agency (“USEPA”) have developed test procedures to determine regulatory compliance. Representative vehicles are subjected to the test procedures and evaporative emissions are measured. Typically, proof of compliance and accompanying certification of an evaporative system for a vehicle line is based upon whether the quantity of evaporative emissions of the vehicle measured during the test procedures falls below a mandated threshold. A typical test procedure includes vehicle preparation, wherein the canister is preloaded with a volume of hydrocarbons, and a preparatory cycle, wherein the vehicle is operated for a predetermined cycle. The vehicle is then subjected to a soak cycle, wherein the vehicle is soaked for a predetermined amount of time in a sealed chamber. During the soak cycle, the vehicle is subject to diurnal temperature variations that range from 65° F. (18° C.) to 105° F. (40° C.) for the ARB test procedure, or 72° F. (22° C.) to 96° F. (36° C.) for the USEPA test procedure. Evaporative emissions are collected from the sealed chamber, measured and analyzed during the course of the test to obtain an emissions value. One test procedure is called a two-day diurnal, wherein the vehicle is operated over a preparatory cycle and then soaked for two days in a sealed chamber. Another test procedure is called a three-day diurnal, wherein the vehicle is operated over a preparatory cycle and then soaked for three days in a sealed chamber. Current evaporative emissions thresholds mandated from ARB and USEPA require that a passenger car emit less than 2.5 grams of hydrocarbon vapors during a two-day diurnal test. The evaporative emissions thresholds mandated from the USEPA include a Tier 2 emissions standard, wherein a passenger vehicle must emit less than 0.95 grams of hydrocarbon vapors during a three-day diurnal test. New evaporative emissions standards from the ARB include a LEV II standard, wherein the threshold mandated for a passenger vehicle is 0.5 grams of hydrocarbon vapors measured during a three-day diurnal test. The ARB also has a PZEV standard, wherein the threshold mandated for a passenger vehicle is 0.35 grams of hydrocarbon vapors measured during a three-day diurnal test plus a two-day diurnal test. The PZEV test procedure includes a rig test of the evaporative emissions systems, which comprises assembling the components of the fuel system including the fuel tank, canister, fuel lines and fuel injection system onto a cart. The rig is subjected to the three-day diurnal test plus the two-day diurnal test, and the rig must emit less than 54 milligrams of hydrocarbon vapors to pass the PZEV standard.
Evaporative canisters designed to meet the Tier 2 and LEV II emissions standards typically comprise conventional elements of a canister, as previously described. Evaporative canisters designed to meet PZEV emissions standards include conventional canister elements, and add some form of hydrocarbon scrubber device. The hydrocarbon scrubber is typically a ceramic monolith device added to the air inlet of the canister to capture and adsorb low-level hydrocarbon bleed emissions that may occur during the test procedure. The addition of the hydrocarbon scrubber increases the complexity of the canister and adds cost. The hydrocarbon scrubber must be packaged into allotted vehicle space and meet all other emissions and safety standards.
Only certain quantities of vehicles are required to meet the stringent PZEV standards. Therefore vehicle manufacturers are reluctant to burden all vehicles with the added cost and complexity that is incident to meeting PZEV requirements. This requires that the vehicle manufacturer be able to design and validate more than one canister package for a vehicle line. In addition, each manufacturer must select and assemble more than one canister package into a vehicle during vehicle assembly process. The addition of components such as the scrubber may complicate the assembly process by adding or changing assembly procedures, depending upon the specific canister required.
Therefore, there is a need to provide a common package for an evaporative canister used on a device, such as a motor vehicle, intended to meet various emissions regulations. There is a need to reduce package and tooling costs for evaporative canisters, and provide flexibility in packaging. There is a further need to provide a canister package with an interchangeable cartridge, wherein the cartridge selected for use in the canister is determined based upon regulatory requirements of the device. A common canister package with an interchangeable cartridge simplifies packaging and assembly of the canister into any device. A common canister package reduces need for testing, development and certification associated with use of multiple canister packages on a common vehicle platform.